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Tuesday, 31 January 2012

Bisphosphonates and side effects

It's generally accepted that bone tumours - whether from primary tumours like osteosarcoma or from metastatic disease - are hard to deal with. Bone cancer pain is difficult to control, and bone tumours can cause fractures and other significant problems, so finding a way of controlling these tumours is essential. To this end there is a whole class of drugs called bisphophonates which are emerging into general oncological practice. These drugs have been found to be effective in slowing the spread of bone tumours, and in helping deal with the pain that they induce. In terms of primary bone cancers, a number of trials are on-going in which these bisphophonate drugs are being used alongside the standard treatments for osteosarcoma. And, as an added bonus, there is evidence that the newer bisphosphonates such as zoledronate and ibandronate, have direct anti-tumour and immune-boosting effects too.

However, there is a big risk that comes with these drugs, which originated as treatments for osteoporosis, and that is a condition called osteonecrosis of the jaw (ONJ). This condition, which occurs in a small subset of patients can cause severe lesions in the jaw, and which can, in a very few cases lead to the crumbling of the jaw. To date there has been no way of knowing which patients are likely to get ONJ, which is a worry for patients taking them, and of course a concern for doctors who prescribe them.

But there may be some good news on the way. Researchers at the Columbia University College of Dental Medicine have done an analysis of patients who developed ONJ, looking at whether or not there is a genetic component to it. And it does appear that this is the case, with variations in a gene called RBMS3 being associated with the occurence of ONJ. This means that in time a genetic test will become available which will help doctors predict which patients are more or less likely to develop ONJ. If it means that doctors will become more confident in prescribing bisphosphonates to cancer patients who need it, then that's really good news.